Length bar for micrometer gauges and the like



Jan. 6, 1948. L. E. GLOVER 2,433,988

LENGTH BAR FOR MICROMETER GAUGES AND THE LIKE Filed July 28, 1944 Patented Jan. 6, 1948 UNITED STATES FFICE '2,433,98'8'6* Y minera sie "njmciiiieieit cauces" ANDYTHE LIKE Lednara Einest'l-icloter, Leatherhead; l'liglaiagl: assignery tov himself and? Pitt'il Gauge? dtlreeV cision Tool Co. Limited, Leatherhead,-England;v a companypf'Great Britain @sieste i 6 claims. (01.5 i-iit 1 This invention relates to linear-dimension Vgauges an'd it refers more particularly'tca length bar for use as or with a linearldi'mensin gauge'.

Such length bars may. be employed with a micrometer end to enable one such micrometer end tofbeused in gauges of varying lengths.v

The length barsareprovided in varying lengths so that by securing two or moretogether any desired length of gauge may beproduced. The ends of each' bar are Careul-Iylapped and when-two length bars are secured the'adjacent lapped faces accurately bed together. Various constructions are known for effecting the securing together of adjacent length bars and particularly desirable constructions are described in the specification of the copending application Serial No. 546,992.

In handling the length bars their dimensions may be affected by the heat of the hands or the body of the user and in order to overcome such difliculties it has been proposed to provide the bar with a protective covering which may be of either a heat insulating or non-insulating material.

According to the present invention a length bar for use as or with a linear-dimension gauge has a surrounding protective tube so mounted as to be spaced from the face of the bar. An air gap is thus formed between the tube and the bar which will prevent transmission of heat between the protective tube and the bar.

Preferably the protective tube is mounted to have slight longitudinal and/or circumferential movement in relation to the bar.

One form of length bar according to the present invention and for use with an internal micrometer gauge will now be described by way of example and with reference to the accompanying drawing which shows the length bar partly in section.

The length bar comprises a piece of steel tube I of definite and accurate length between its end faces 2, 3. These faces are hardened and are lapped to produce great accuracy. The bar is provided at its ends with means for attachment to another bar. Thus, for example, it has one end internally threaded at 4 and a threaded plug member 5 mounted at the other end. Said threaded plug member is illustrated as having freedom of movement in all directions and is of the form described in the specification of the copending application Serial No. 546,992. A ferrule Il, which may be of metal but is preferably tapered'lpin,-fI'Ilipassing/through holes inthe wall I oftheferruleand holes in the wall of thetube. The? h ole fliviler wall 0f.; the tube are Slightly larger-thanfthe pin so that distortion in assemblingisf plv eveliefl-v .Thxafdjafllienl 0f the ferrules are recesd am!lfiofaccommgdaiea prQteCtii/e. tube |2- Thii tubefis TVpreferfalply of heat-insulating material, Suchet bitumenised .peper mit it Will be understood @dobber-.materials mi* be employed y The diameierfofihe recesses is sushihai the Protec* tive tube will have slight play therein and the length of the tube is a little less than the distance between the bottoms of the recesses in the ferrules as is shown in the drawing. The tube can thus move circumferentially and also slightly longitudinally in relation to the bar. The internal diameter of the tube I2 is greater than that of the bar I so that an air gap 6 is formed between the tube and the bar. In this way when the bar is handled heat of the hands or the body of the user will not be transmitted directly to the bar. Further, as the protective tube is free in relation to the Vbar the latter can only be assembled with like bars by handling by means of the ferrules 9. This avoids twisting or distortion of the length bars, particularly the longer ones. By arranging for the tube I2 to have a slight movement in re' lation to the bar any change in the length of the tube due to change of temperature or humidity conditions will not be transmitted to the bar itself.

The length bar may be used with all kinds of length measuring apparatus, such as micrometer gauges in which the position of an anvil or like bearing surface is controlled by a screw or by other means such as a pack of accurately dimensioned blocks, for example slip gauges, or in which it is movable and attached to indicating mechanism.

What I claim is:

l. A length bar for use in gauging lengths, means carried on said length bar for connecting it to another gauging member, said length bar having the end faces thereof accurately finished in a plane at right angles to the axis of the bar, and a protective tube surrounding said length bar and spaced therefrom to provide an air space between the bar and the protective tube, and said protective tube being mounted in such manner that it is capable of movement relative to the length bar.

2. A length bar for use in gauging lengths,

. 3 means carried on said length bar for connecting it to another gauging member, said length bar having the end faces thereof accurately nished in a plane at right angles to the axis of the bar, and a protective tube surrounding said length bar and spaced therefrom to provide Van air space between the bar and the protective tube, and said protective tube 'being mounted in such manner j that it is capable of longitudinal and circumferential movement relative to the length bar.

3. A length bar for use in gauging lengths,

means carried on said length bar for connecting it to another gauging member, said length bar' a protective tube loosely supported at its ends in the recesses provided in the ferrules, to thereby having the end faces thereof accurately nished in a plane at right angles to the axis of the bar,

surrounding said length bar and spaced Wthereff from to provide an' air space between the bar and and a protective tube of heat insulating material provide for longitudinal and circumferential movement of the protective tube relative to the bar.

6; A length bar according to claim 5, wherein 1 the-ferrules are fitted on the bar by means of pins the protective tube, and said protective tube beingl mounted in such manner that it is capable of movement relative to the length bar.

4. A length bar for use in gauging lengths, means carried on said length bar for connecting it to another gauging member, said length bar having the end faces thereof accurately finished in a plane at right angles to the axis of the bar, and a protective tube of heat insulating material surrounding said length bar and spaced therefrom to provide an air space between the bar and the protective tube, and said protective tube being mounted in such manner that it is capable of passing through slightly larger holes in the bar.

LEONARD ERNEST GLOVER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 689,389 Eckelt Dec. 24, 1901 857,810 Kohlhaas June' 25, 1907 FOREIGN PATENTS Number Country Date 325,963 Great Britain Mar. 6, 1930 

